De Broglie–Bohm pilot wave theory

Thenewdeal38

"Imagine what happens if you take two particles that can be located anywhere on 1 meter radius (you don't know where) and you try to move them closer. It's strange but from the observations you get interference (constructive or destructive depending on the distance between the two)."

Could it be that each particle emits a curciular wave like gravity. And the interference is the collision of two wave like gravitys colliding into each other?

But since photons dont have mass like electrons do they also emit a gravitational feild?

Thenewdeal38

"A dramatic series of experiments emphasizing the action of gravity in relation to wave–particle duality were conducted in the 1970s using the neutron interferometer.[14] Neutrons, one of the components of the atomic nucleus, provide much of the mass of a nucleus and thus of ordinary matter. In the neutron interferometer, they act as quantum-mechanical waves directly subject to the force of gravity. While the results were not surprising since gravity was known to act on everything, including light (see tests of general relativity and the Pound-Rebka falling photon experiment), the self-interference of the quantum mechanical wave of a massive fermion in a gravitational field had never been experimentally confirmed before."

atomthick

I don't think gravity has something to do with it. For example in your question the ball can't get through the double slit unless you move the wall very close to the ball (because the ball has a very short wave length therefore it's localized in a very short range of space). If gravity was to play a part in this then wave length would be larger because the ball has a bigger mass.

Thenewdeal38

exellent point

Thenewdeal38

"the ball can't get through the double slit unless you move the wall very close to the ball"

Still I dont thinks this is possible. Even if you put the ball right up against the slits and had a machine that pushed the ball against those slits.

Even if you created a vaccum system Im pretty sure it wouldnt work.

jambaugh

Before picking interpretations I suggest you study more the actual physics.

In your steel balls example let me point out that to observe quantum phenomena you'll need to cool the balls down to absolute zero, and carry out many many experiments to see the interference pattern in the distribution of where the balls end up.

Your description of what non-Bohmian interpretations say or predict is inaccurate. Note this most of all, the various interpretations make no distinction about what we will physically observe in the laboratory and thus are not competing theories, only competing philosophical points of view about what if anything is going on behind what we can see.

Thenewdeal38

But particles move in a wave like motion right?

Thenewdeal38

People on this forum are saying that the moon isnt there when it isnt being observed! And they say that the copenhagen interpretation proves it. How is this not a non-Bohmian interpretation.

Anyways
"Waves are shown to be the only means of describing motion, since smooth motion on a continuum is impossible. If a particle visits every point on its trajectory then the motion is an algorithm for each point. Turing[29] has shown that almost all numbers are non-computable, which means that there is no possible algorithm, so the set of points on a trajectory is sparse. This implies that motion is either jerky or wave-like. By removing the need to load the particle with the properties of space and time, a fully deterministic, local and causal description of quantum phenomena is possible by use of a simple dynamical operator on a Universal Invariant Set. Evidently, quantum particles are indeed particles, but whose behaviour is very different from classical physics would have us to expect."

"By removing the need to load the particle with the properties of space and time" This is the only part that confuses me. Can someone explain what they mean by this?

jtbell

Who among us here who as actually studied QM seriously has said that? Link to a specific post, please.

DrChinese

You're right. It really happens like you say. The ball moves up and down like a wave and goes through the slit, forming an interference pattern.




Just kidding.

DrChinese

As jtbell points out, this is not a statement being made by physicists. You are confusing Einstein's analogy with a literal comparison. Particles do NOT* have well-defined PROPERTIES independent of the act of observation. So the better analogy is that the Moon is not yellow when it is not being observed - it is only yellow when observed as such. But it is still somewhere at all times.

*Keeping in mind this is interpretation dependent.

jambaugh

People on this forum say lots of things between utter nonsense and profound truth...just as in the rest of the world. If you're going to cite "people on this forum" it would do well to be more specific. Others can then determine if they indeed are uttering nonsense or if you are misreading what they are saying, (or --of course-- if you and/or they are uttering profound truths.)

As far as what the Copenhagen interpretation says, that too can depend on who you ask. As I understand it, CI rejects the postulate of a fundamental objective reality.
Understand then that when referring to "reality" one is invoking a classical model and not asserting an ontological position. I find it helps to replace the word "reality" = "what is" with "actuality=what happens".

In that sense it is just as wrong to assert that the moon ceases to exist (in an objective state) when not observed as it is to assert that the moon continues to exist (in an objective state) since either statement is presupposing facts not in evidence through empirical observation.

What CI rejects is statements about the Moon's state (or an electron's) apart from statements linked to observational events.
"The moon is there = There is the moon!",
"The moon is not there = I see a space where the moon used to be!"

Who are you quoting here?

thenewmans

Thenewdeal38, I’m glad you like the De Broglie–Bohm theory. It’s my favorite too. But I intentionally took a while to settle on it. I felt that if I picked one it’s because of belief since I really didn’t know enough. Even now I know that my choice is still just a matter of taste. There are many PF members here with an actual physics degree that prefer many worlds. And many more prefer Copenhagen. And out of those, there’s a bunch that prefer “Shut up and calculate.”
http://www.physicsforums.com/poll.ph...ts&pollid=1995
They all have their reasons. Einstein certainly had his reasons for saying, “I refuse to believe that the moon does not exist when we don't observe it.” But this was an extreme generality used in a much more nuanced argument. I think I recall Bohr had better language for these non-classical physics type discussions.

I’ll give you an example. I have been performing an experiment on my wife. Each day I wake up, I check to see if my wife is still alive and then I make a note of it. I did this 100 times and each time she was alive. I tried some statistics and I thought maybe she will live forever. But maybe my sample size isn’t large enough. So I did it 500 times and then 1000. I now have collected 5000 observations and I can now tell you with absolute certainty that my wife will live forever. What is wrong with my logic?

Here’s another one: What exactly are the properties of an electron before you measure them? This question has a totally different meaning when you’re talking about classical physics and when you’re talking about quantum mechanics.

So I think you should reconsider jambaugh’s suggestion for a little longer.

Science proves nothing, not a thing. It can only tell you the likelihood. Principals and laws tell you what's really really likely. But they are still not proof.

Just to be clear, (JTBell and DrChinese, please correct me if I’m wrong), according to any interpretation of QM, there is a very, very, VERY remote possibility that the entire moon truly is no longer there just when you are not looking at it. Who could possibly imagine an entire BB, let alone the moon blinking out of existence. It’s a very remote possibility but it’s still possible. So how do you know that hasn’t happened if you don’t look out the window? (Caution: I have not actually studied QM seriously.)

If you’re ready to have your noodle cooked even more, then you should look into quantum tunneling.
http://en.wikipedia.org/wiki/Quantum_tunneling
And this!
http://en.wikipedia.org/wiki/Casimir_effect

jambaugh

Before asserting and trying to calculate such probabilities first understand that even within the wacky world of QM conservation laws still hold. The moon can't "just disappear" (probability = 0). The energy/momentum/angular momentum (lepton number...) must end up somewhere. There is I suppose a roughly calculable extremely small non-zero probability that say the nuclei of every atom making up the moon spontaneously decays or something.

thenewmans

OK well I wasn't thinking decay. I was thinking Heisenberg uncertainty principle. Isn't that what Einstein was referring to when he said, "I refuse to believe...?" I'm having trouble finding the quote now. (http://en.wikiquote.org/wiki/Albert_Einstein) So each particle of the moon has a probability cloud that is not limited by extent. So at any moment, you can calculate the probability that a particle is positioned somewhere far away. It's a small probability. And the chances of 2 particles far away is even smaller.

Ken G

The way I would put it is, quantum mechanics appears to rely for its very existence as a theory on two very surprising types of duality-- wave/particle duality, and determinate/indeterminate duality. The former gets more press, but the latter is just as important. Wave/particle duality is actually a form of unification, though some people for some reason seem to abhor it (despite the fact that unification has always been a top priority of physics). Determinate/indeterminate duality can also be thought of as a unification, but is rarely considered that way simply because we never really recognized the role of indeterminacy in physics prior to quantum mechanics. I believe that was simply a form of denial on physicsists part-- they didn't need to worry about indeterminacy because it never had to be included in the theory before, but it was certainly always there in practice.

So, when one says that the Moon is not a wave, or that the Moon is not indeterminate, one is simply saying that the Moon is not a good place to study those two dualities. It just isn't the place where the dualities are important. But the theory of QM certainly has no problem with the dualities being present there, just as Newton's theory of gravity had no problem with gravity being present between the constituents of an atom-- it just never mattered and could not be directly tested in that context.

PhilDSP

Interesting comments. In his last book "Nonlinear Wave Mechanics" (in English anyway) de Broglie is of the opinion that at least some of the indeterminacy in QM is due to the use of linear mathematics (required for Hilbert Space and Fourier Analysis for example) while the interaction of charge and/or other possible sub-components of particles with a field may be governed by processes which are essentially non-linear. At least that is what I got from a very quick read of some parts of the book.